ES2661294T3 - Apparatus for heating and transferring metallic materials for a fusion plant and method for melting metallic materials - Google Patents

Abstract

Apparatus for heating and transferring mainly metallic materials to a melting furnace (12), said apparatus comprising a conveyor device (13) configured to move said materials continuously to said melting furnace (12), wherein said conveyor device (13) is choose from a group comprising a conveyor belt, a plate conveyor belt, a mobile board belt, a rotating chamber or a possible combination of the above, wherein said conveyor device (13) is provided with a closed chamber (24 ) for the passage of said metallic materials, characterized in that it comprises at least one induction heating unit (28) comprising at least one coil (29) mounted externally to said conveyor device (13) and suitable for generating an induced magnetic field in said materials for electromagnetic induction heating said materials, which move in said transpor device tador (13), at a temperature between 300 ºC and 800 ºC, and in any case keeping them in a solid state.

Description

Apparatus for heating and transferring metallic materials for a fusion plant and method for melting metallic materials 5

Field of the Invention

The present invention relates to an apparatus for the transfer of heat and metal materials for a fusion plant and to a fusion plant comprising said apparatus.

The heating and transfer apparatus is provided with means for heating the metallic materials before they are introduced into a melting furnace.

The present invention can be applied advantageously, but not exclusively, for the production of steel or cast iron.

Background of the invention

In the field of iron and steel manufacturing, melting vessels, also called melting furnaces, for the production of liquid metal are well known.

Melting furnaces are usually fed with solid materials that contain a high concentration of the metal to be produced. The final composition of the liquid metal is adjusted by adding other metallic or non-metallic compounds and very often with materials that have a high carbon content.

25 Melting and refining furnaces in general can be divided into two types:

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electric furnaces that use electric energy as an additional energy source to the chemical energy generated by the fusion processes;

-

heating furnaces that do not use electrical energy and use only heat sources; if additional energy is required in addition to the chemical energy produced by the refining reactions, for example, burners are used.

The types of electric furnaces used most often can comprise electric arc furnaces, furnaces

35 induction, resistance furnaces. A variant of electric arc furnaces, with respect to the production of iron alloys, is the submerged arc furnace.

The heating furnaces may comprise oxygen converters, Martin-Siemens furnaces and cupola furnaces.

After the primary melting stage of the metal, a refining stage is provided. Usually different alloy materials are added to the molten material, to obtain the required chemical composition.

In all these processes, during the melting and refining stages, all or only some of the materials that are

45 funden can be downloaded. The melting and refining stages are also called "ignition load" and correspond to the time during which heat / electrical energy is supplied to the melting furnace.

During this stage, the materials can be loaded into the melting furnace by means of a conveyor that adjusts their delivery speed.

During the ignition load, the limitation of the supply speed depends on the specific heating energy requirements for the fusion: the higher the specific fusion energy required, the lower the supply speed and the productivity of the melting furnace.

55 To reduce the duration of the melting process, it is also known to heat the material before it is loaded into the melting furnace.

A well-known technology for heating the metal material exploits the principle of magnetic induction.

The magnetic induction heating technique is normally used in the fields of fusion, heat treatments, molding and welding.

An example application of the magnetic induction heating technique, with respect to the melting process of metallic materials, is the induction furnace.

65 An induction furnace may consist of a melting vessel, usually made of ceramic material, with a

cylindrical shape and to which induction heating devices are associated. Induction heating devices typically comprise at least one coil disposed around the melting container, which is powered by alternating current at a suitable frequency. The coil may consist of a spirally wound tube in which a cooling fluid, usually water, is circulated to preserve the

5 mechanical resistance properties thereof.

The alternating electric current flowing in the coil generates an alternating magnetic field induced in the fusion vessel and generates induced currents in any conductive metal material that is struck by the induced magnetic field. The currents induced in the conductive metallic material in turn generate thermal energy

10 due to the Joule effect.

With respect to the technique of heating a mass of metal by induction, the metal product can be heated by means of longitudinal flow induction or transverse flow induction.

In the case of longitudinal flow induction, the coils and magnetic yokes, which are part of the heating devices, are arranged in such a way as to concentrate the induced magnetic field along the longitudinal development of the material to be heated. In this case, the heating of the metallic material occurs along the axis of the coil. A similar example of heating of the metallic material, by the action of the longitudinal magnetic field, is that which occurs in an induction melting furnace.

In the case of transverse flow induction, the components of the heating device are arranged on opposite sides of the metal material to concentrate the oscillating magnetic field through the material to be heated. In this case, the main heating action occurs on the surface of the metallic material.

With respect to the heating of the metallic material before it is loaded in a melting furnace, a process and a plant are known, for example, from US-A-4,403,327, in which the scrap or other Metallic material is first heated by induction in a first container and then loaded into a second container for melting, the induction principle exploding again.

The metal material leaving the first container is still in a solid state and is transferred to the second container, for example, by loading baskets.

The loading baskets provide a direct, uncontrolled and immediate feeding of the metal material directly into the second container.

35 This is particularly disadvantageous, since it is not possible to adequately and continuously control the ways in which the metallic material inserted into the oven is introduced throughout the melting process.

In fact, continuous monitoring of the amount of material inserted would prevent the molten metal mass from being subjected to drastic temperature reductions.

US 3,413,401 A describes a vertical receptacle, heated by induction means to heat and melt the metallic material, which is poured into its molten state in a lower container.

45 EP 2,546,592 A1 describes a transport system for metallic material to a melting furnace, in which there are radiation heating burners along the conveyor. The use of such radiation burners has the disadvantage that it heats the material only on the surface and, if high temperatures are used, it can lead to the melting of any material of small size, with the consequent adhesion and the corresponding damage to the system of transport and a slowdown in the production cycle.

One of the purposes of the present invention is to obtain an apparatus for heating and transferring metallic materials that allows the melting cycle times to be reduced.

Another object of the present invention is to obtain an apparatus for heating and transferring metallic materials, installable in a melting plant, which guarantees to feed the materials in predetermined modes.

Another objective of the present invention is to obtain an apparatus for heating and transferring metallic materials that allows reducing the complexity of the plant and its manufacture.

Another objective of the present invention is to improve a method for heating and transferring metallic materials to a melting furnace that allows the melting cycle times to be reduced.

The applicant has devised, tested and realized the present invention to overcome the drawbacks of the prior art and obtain these and other purposes and advantages.

Summary of the invention

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other features of the invention or variants of the main inventive idea.

In accordance with the above purposes, an apparatus for heating and transferring mainly metallic materials is configured to heat and transport the metallic materials to a melting furnace for later melting.

According to a feature of the invention, the apparatus comprises at least one conveyor device configured to move materials continuously to the melting furnace.

According to another feature of the present invention, the apparatus comprises at least one induction heating unit associated with the conveyor device and configured to electromagnetic induction heating the materials moved by the conveyor device, in any case, keeping them in a solid state.

With the present invention, therefore, the metallic materials are mainly heated before they are introduced into the melting furnace at a temperature such that they are not brought to a molten state which, therefore, allows reducing the times of each melting cycle

The use of the electromagnetic induction heating technique, compared to other known technologies, allows the intensity of heating of the fed materials to be modulated quickly and accurately, also depending on the process requirements.

25 Therefore, using this technique, it is possible to ensure that the materials, even possibly heterogeneous, are heated, but remain in a solid state that prevents problems in their movement and prevents damage to the conveyor.

In addition, the particular configuration of the heating and transfer apparatus allows the melting furnace to be fed with already heated materials and substantially continuously, or in any case in correlation with the specific requirements of the melting process.

Some embodiments of the present invention also refer to a fusion plant comprising the

35 minus a melting furnace in which mainly metal materials are melted, a loading unit configured to feed the materials, and a transfer heating apparatus as described above, which interposes between the loading unit and the oven of fusion.

Other embodiments of the present invention relate to a method for the fusion of metallic materials 40 which comprises transporting mainly metallic materials, by means of a conveyor device, continuously to a melting furnace for subsequent melting.

The method also provides that during transport of said materials they are heated by electromagnetic induction and kept in their solid state. Four. Five

Brief description of the drawings

These and other features of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of a melting plant for metallic materials, comprising a heating and transfer apparatus according to an embodiment of the present invention; FIG. 2 is a schematic representation of a possible embodiment and of a transfer apparatus according to the invention; Figure 3 is a schematic representation of a variant embodiment of Figure 2; -Figure 4 is a schematic cross-sectional representation of a possible embodiment of the

heating and transfer apparatus according to the present invention; Figures 5, 6 and 7 are schematic representations of possible variants of Figure 4; Figure 8 is a schematic representation of a variant embodiment of Figure 1.

60 For ease of understanding, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that the elements and features of one embodiment can be conveniently incorporated into other embodiments, without further clarification.

Detailed description of some embodiments

With reference to Figure 1, a heating and transfer apparatus, indicated in its entirety by reference number 10, can be installed in a melting plant 11 configured to melt mainly 5 metallic materials and to obtain metallic products with a certain composition.

Mainly metal materials, hereinafter referred to generically as materials, may comprise, for example, scrap fragmented by shearing or grinding and separated from non-metallic contaminants and possible exogenous metals.

The materials can be fragmented into pieces with a size between approximately 50 mm and 100 mm. This level of fragmentation facilitates the transport and dosing of the metallic material.

The fragmented scrap, possibly also heterogeneous, has a high density of lumps, a high

15 concentration of base metal and uniform sizes from piece to piece. These properties make fragmented scrap suitable for induction heating.

The materials may also comprise alloy components suitable for modifying the concentration of the final product to be obtained.

The melting plant 11 according to the present invention comprises at least one melting furnace 12 located downstream of the heating and transfer apparatus 10 and configured to melt the materials fed by the heating and transfer apparatus 10.

25 The heating and transfer apparatus 10 is configured to heat and transfer the material before it is introduced into the melting furnace 12.

According to a feature of the present invention, the heating and transfer apparatus 10 comprises at least one conveyor device 13 configured to move the material to the melting furnace 12 in a direction of movement.

According to another aspect of the present invention, the heating and transfer apparatus 10 also comprises at least one induction heating unit 28 associated with the conveyor device 13 and configured to electromagnetic induction heating the materials moved by the conveyor device 13. The entity from

The heating to which the material is subjected in the heating and transfer apparatus 10 is such that it keeps it in a solid state. Simply by way of example, if the material being heated is scrap, the induction heating unit 28 is configured to heat it at a temperature between 300 ° C and 800 ° C.

The conveyor device 13 is configured to modify, in a continuous and predetermined manner, the speed of supply of material to the melting furnace 12.

By properly coordinating the activation of the conveyor device 13, it is possible to guarantee the feeding of the material to the melting furnace 12 continuously or in accordance with the needs dictated by the

45 individual fusion cycle. In addition, the heating action exerted by the induction heating unit 28 allows the melting process to be adequately controlled, for example, by avoiding sudden variations in the temperature of the liquid bath in the melting furnace 12.

For this purpose, and in accordance with the possible solutions, the conveyor device 13 may be provided with weight control detectors and / or detectors to control the speed of movement of the materials, to determine on each occasion the speed of supply of the material .

According to a possible embodiment, the supply speed sensors can be connected to the conveyor device 13, configured to control the amount of material being transported.

55 The supply speed sensors may comprise TV cameras, photocells, optical, inductive, capacitive, ultrasonic, microwave or radiofrequency sensors.

According to possible embodiments, the conveyor device 13 can be chosen from a group comprising a conveyor belt, a plate conveyor belt, a mobile board conveyor, a rotating chamber or a possible combination of the above.

According to possible embodiments, the conveyor device 13 is designed to meet at least one of the following requirements:

65 -ability to conserve the thermal energy of the transported materials, limiting the effects of the

heat dispersion; -reduce the overheating of the structural parts of the conveyor device 13 due to the induction heating to which the materials are subjected during the movement; -maintain a controlled environment in the conveyor device 13, for example, to limit the interaction of the 5 materials with the air, or to avoid the dispersion of potentially polluting gases in the surrounding environment.

With reference to the embodiments shown in Figures 1-4, the conveyor device 13 may comprise a mobile board conveyor 14.

According to possible embodiments, the mobile board conveyor 14 can have a mainly longitudinal development in said direction of movement D.

The mobile board conveyor 14 can be defined by a channel having a concave cross-section, 15 of the cradle type, to contain inside the materials to be transferred.

According to the possible solutions, the conveyor device 13 may comprise a drive element 16 (figure 1) connected to the mobile board conveyor 14 and provided to feed the material in the direction of movement D.

The drive element 16 can be of the vibratory type, for example, with eccentric masses, and is configured to impart oscillations on the mobile board conveyor 14 in a direction parallel to the direction of movement D of the materials. In particular, the mobile board conveyor 14 is subject to acceleration in an opposite direction with respect to the direction of movement of the materials. The materials

25 contained in the mobile board conveyor 14 are subject, due to their inertia, to sliding on the bottom of the mobile board conveyor 14, in a direction consistent with the direction of movement and feeding of the materials to the melting furnace 12.

The drive element 16 may be attached near the loading or unloading end or in an intermediate position of the longitudinal extension of the mobile board conveyor 14.

According to the possible solutions, the mobile board conveyor 14 can be mounted on suspension elements 15, configured to support the suspended mobile board conveyor 14, and to allow it to oscillate as described above and due to the actuation of the drive element 16 .

35 According to possible implementations, the suspension elements 15 may comprise at least one of tension bars, elastic elements, damping elements, pivoting elements, support plates or possible combinations thereof.

With reference to the embodiments shown in Figures 2 and 3, the suspension elements 15 may comprise tension bars attached to the peripheral edges of the mobile board conveyor 14 and be provided to support the loading of the transported materials. The first ends of the tension bars are attached to the upper edge of the mobile board conveyor 14, while their opposite ends can be attached to a fixed structure of the conveyor device 13. The pivoting elements can be associated with the ends of

45 the tension bars to allow the mobile board conveyor 14 to swing.

According to the embodiment shown in Figure 4, the suspension elements 15 comprise a support platform 17 configured to support the mobile board conveyor 14, and support elements 18 connected to a fixed part of the conveyor device 13 and to the platform support 17 and configured to support the latter.

The support platform 17 and / or the mobile board conveyor 14 may comprise guiding elements to guide the oscillation to which the mobile board conveyor 14 is subjected due to the activation of the drive element 16.

55 The mobile board conveyor 14, parts thereof, or structural components of the conveyor device 13 can be made of materials that have low magnetic permeability and low electrical conductivity. A material with these properties allows to reduce the overheating of the structural components due to the heating action of the induction heating unit 28. Simply by way of example, the use of austenitic stainless steel can be provided.

The mobile board conveyor 14 may be associated with cooling devices, for example, water spray type or water mist type, to preserve the mechanical strength properties of the mobile board conveyor 14.

65 According to possible embodiments, the structural parts of the mobile board conveyor 14 can

be coated with a heat insulating and wear resistant coating. According to the possible embodiments, the heat insulating coating can be a ceramic or refractory material.

According to possible embodiments, instead of a mobile board conveyor, the conveyor device 5 may comprise a plate conveyor belt 19 (figures 5, 6 or 7) provided to move the materials in the direction of movement D.

The plate conveyor 19 can comprise a plurality of plates 20, reciprocally connected to each other and configured to define the bottom of the plate conveyor 19 and the support surface 10 of the materials.

The plates 20 are supported by a plurality of rollers 53 on which the plates 20 move in the direction of movement D.

The plates 20 can be substantially flat, as shown, for example, in Figures 5, 6 and 7, or concave, for example, in a U-shape, where their concavity defines a channel for containing the materials to be transported. .

If the plates 20 have a substantially flat shape, the plate conveyor 19 can comprise 20 side walls 21 arranged near the side edges of the plates 20 and defining therewith a transport channel 22 for the materials to be moved .

According to possible embodiments, the side walls 21 can be fixed with respect to the plates 20, for example, mounted on a fixed structure of the conveyor device 13.

25 The plates 20 and / or the side walls 21 may be made of a material that has low magnetic permeability and low electrical conductivity. Simply by way of example, the plates 20 may be made of austenitic stainless steel.

The cooling devices may be associated with the plates 20 and / or the side walls 21, for example, of the type of water spray or of the type of water mist.

In accordance with possible embodiments, the structural parts of the conveyor device 13, and the possible plates 20 and / or the side walls 21 can be coated with a heat insulating and wear-resistant coating 35. According to the possible embodiments, the heat insulating coating material may be a ceramic or refractory material.

According to possible embodiments, a closing body 23 may be associated with the conveyor device 13 described with reference to Figures 1 to 7, and is configured to define, alone or in combination 40 with parts of the conveyor device 13, a chamber closed 24 for the passage of said materials with controlled environmental conditions.

In particular, the closure body 23 may be suitable for sealing the moving materials, and to prevent them from coming into contact with the air, which can oxidize the moving materials.

In accordance with possible embodiments (Figure 1), the closure body 23 may comprise a box-shaped tube 25, inside which at least the conveyor device 13 is disposed. In this case, the tube 25 itself defines the camera 24.

50 According to other embodiments (Figures 4 to 7), the closing body 23 comprises a cover element 26 configured to define, together with the conveyor device 13, the chamber 24 containing the materials.

In particular, with reference to Figure 4, the cover element 26 is connected to the upper part of the mobile board conveyor 55, to close the concavity defined in this way.

The cover element 26, together with the mobile board conveyor 14, defines the transport volume of the materials.

60 It is quite evident that, in order to ensure a homogeneous distribution of heat over the metal load, the height of the material bed must be limited and uniform.

According to the embodiments shown in Figures 5 to 7, the cover element 26 is connected to the upper part of the side walls 21, in order to define together with the latter and with the plates 20, the chamber 24 that contains and transfers the materials.

In accordance with possible embodiments, the injection devices can be arranged inside the chamber 24, configured to introduce a fluid or gas, inert or reducer therein, suitable for conditioning the environmental conditions in the chamber 24. This allows avoiding the oxidation of the heated materials that are passed through the conveyor device 13. According to possible solutions, the device for

The injection may comprise a plurality of injectors, installed in the conveyor device 13 in different positions along its longitudinal extension.

According to a variant embodiment, which may possibly be combined with the embodiments described herein, the conveyor device 13 may be provided with a suction apparatus 27 configured to generate a depression in the chamber 24 and to contain the effects of oxidation of the transported heated metal.

According to possible formulations, the suction apparatus 27 may comprise a fan configured to control the depression within the chamber 24.

15 The suction apparatus 27 may be provided with filter elements configured to filter the gases taken.

The suction apparatus 27 may in turn be connected to an apparatus for treating gases, suitable for the treatment of incoming gases.

The closure body 23 may be designed following at least one of the following criteria:

-

manufacture at least its structural parts using materials with low magnetic permeability, to guarantee at least its mechanical seal; - reduce the thickness of at least the electrically conductive materials that make up the structural parts 25 of the apparatus; -cover the surfaces of structural parts potentially exposed to transported materials

hot with insulating materials; -Sealing tightly the connections and interface areas between the different components; -install the induction heating unit 28 as close as possible to the transported materials.

In accordance with possible embodiments of the present invention, the induction heating unit 28 comprises one or more coils 29 mounted outside the conveyor device 13 and suitable for generating a magnetic field induced in the materials.

Each induction heating unit 28 also comprises at least one electric power generator 31 electrically connected to one or more of the coils 29 to supply them with the electrical energy necessary to generate the magnetic field.

The electric power generator 31 may comprise a frequency converter suitable for varying the frequency and controlling the current of the coils 29.

According to possible embodiments, the electric power generator 31 can be configured to supply an alternative electric current with a frequency between 300 Hz and 1,500 Hz. According to a variant embodiment, the electric power generator 31 can be configured to supply a

45 alternative electric current of less than 3,000 Hz.

In accordance with possible formulations of the present invention, and as mentioned above, the heating and transfer apparatus 10 may comprise several induction heating units 28 associated with the conveyor device 13 in different positions along the longitudinal extent of this latest. In this way, it is possible to differentiate the heating action on the material in the conveyor device 13 in different positions of the latter.

This makes it possible to differentiate the heating entity along the longitudinal extension, also depending on the amount of materials contained in the conveyor device 13, or to determine a gradual heating

55 of the materials.

According to the possible embodiments, to control the temperature of the materials in the conveyor device 13, the temperature sensors are associated with the latter.

The temperature sensors may be installed along the walls of the mobile board conveyor 14

or the side walls 21 of the plate conveyor belt 19, possibly protruding into the lined wall.

According to a possible solution, for example, shown in Figures 1 and 2, the coils 29 are defined by a plurality of spirals 30 wound around a common axis and arranged near the conveyor device

13.

According to possible formulations of the present invention, the coils 29 may be made of an electrically conductive material, for example, copper.

The coils 29 can be defined by one or more tubes in which a cooling fluid is caused to flow to control the temperature that the material of the coils 29 can reach.

The coil 29 may be formed by a single layer of spirals 30, as shown, for example, in Figure 2,

or it can comprise several layers, rolled on top of each other.

According to possible formulations of the present invention, the spirals 30 of the coils 29, or at least some of them, can be mechanically attached to a fixed structure, for example, against walls of the conveyor device 13, to contain the forces of electromagnetic repulsion acting on the coil

29.

15 According to possible embodiments, the spirals 30 of the coils 29 may be electrically isolated.

The coils 29 can be mounted, with respect to the conveyor device 13, to generate a magnetic field with:

-

longitudinal flow lines, that is, parallel to the direction of movement D of the materials (shown, for example, in Figures 1 and 2); -transversal flow lines, that is, transverse with respect to the direction of movement D of the materials (shown, for example, in Figures 3 to 7).

25 According to a first embodiment, shown, for example, in Figure 2, the coil 29 is wound around and externally to the conveyor device 13, in this case around the mobile board conveyor 14, and in accordance with an axis winding of the spirals 30 substantially parallel to the direction of movement

D. In this embodiment, a magnetic field is generated with longitudinal flow lines.

According to another embodiment, shown, for example, in Figure 3, the induction heating unit 28 comprises at least two coils 29, facing each other and between which the conveyor device 13 is interposed. In particular, the coils 29 are arranged with their winding shafts substantially transverse to the direction of movement D of the materials. In this embodiment, it

35 generates a magnetic field with transverse flow lines.

According to possible formulations of the present invention, for example, which are shown with reference to Figures 4 to 7, the induction heating unit 28 may comprise at least one magnetic field concentrating device 32 around which said coils are wound 29. The magnetic field concentrator device 32 is suitable for concentrating the magnetic field towards said advancing materials.

The magnetic field concentrator device 32 may comprise at least one of magnetic concentrators or yokes.

The magnetic field concentrator device 32 can be made with materials that have high magnetic permeability and, therefore, can increase the overall heat transfer efficiency.

The magnetic field concentrating device 32 can be made with laminated metal sheets configured to reduce the magnetic resistance of the magnetic circuit, or with magneto-dielectric materials.

According to a first solution, shown, for example, in Fig. 4, the magnetic field concentrator device 32 is arranged above the conveyor device 13 and is configured to concentrate the magnetic field in an orthogonal direction to the direction of movement of the materials.

55 In one solution, the magnetic field concentrator device 32 comprises a concentrator body 33 with a mainly longitudinal development and located during use parallel to the direction of movement D.

The concentrator body 33 has an E-shaped cross-section, that is, it has at least two cavities 34 separated from each other by a ferromagnetic separation portion 35.

A coil 29 is wound in the concentrator body 33, so that the spirals 30 are arranged in the cavities 34 and are wound around the separation portion 35.

By electrically feeding the coil 29, the spirals 30 that form the coil 29 generate field lines

65 magnetic concentrates that leave the separation portion 35 in a direction parallel to the winding axis and affect the materials arranged below.

With reference to Figure 5, another embodiment is described comprising at least two magnetic field concentrating devices 32, similar to that described with reference to Figure 4.

In particular, in this case, the two magnetic field concentrating devices 32 are arranged

5 facing each other, and the conveyor device 13 is interposed between them. In the solution shown in Figure 5, each magnetic field concentrator device 32 is located laterally adjacent to the side walls 21 of the mobile board conveyor 14. Both magnetic field concentrator devices 32 are configured to emit respective magnetic field flows substantially parallel to each other and orthogonal in turn to the direction of movement D of the materials.

According to other embodiments of the present invention, which are shown, for example, in Figures 6 and 7, the magnetic field concentrating devices 32 comprise a yoke 36 made of ferromagnetic material around which the coils 29 are wound.

According to the embodiments of Figures 6 and 7, the yoke 36 of ferromagnetic material is substantially C-shaped, or has a substantially C-shaped cross section.

During use, the yoke ends, also called polar ends 37, are oriented towards the metal materials present in the conveyor device 13.

The spirals 30 of the coils 29 can be adequately protected by installing a magnetic screen that acts as a concentrator to increase induction efficiency.

According to the solution shown in Figures 6 and 7, two coils 29 are each arranged near one of the 25 polar ends 37 and another coil 29 is located in an intermediate position of the longitudinal extension of the yoke

36.

Figure 6 shows a solution in which both polar ends 37 are disposed above the moving materials.

Figure 7 shows instead a solution where the polar ends 37 are arranged laterally to the conveyor device 13 and each facing one of the side walls 21.

According to possible embodiments, shown, for example, with reference to Figures 1 and 8, between the

35 heating and transfer apparatus 10 and the melting furnace 12 an introduction element 38 is interposed, configured to allow the introduction of the heated material into the melting furnace 12.

The introduction element 38 may comprise, for example, a slide, located above the smelting furnace 12 and which allows the material to be heated to be discharged by gravity to the melting furnace 12.

According to possible embodiments, the introduction element 38 can be connected to a selector device 39 provided to take the introduction element 38 at least in a first operative position to discharge the material in the melting furnace 12 and a second operative position .

The second operative position of the introduction element 38 may correspond to a position of non-interference of the latter with moving parts of the melting furnace 12, such as, for example, the roof covering the housing of an electric oven.

According to a variant embodiment, for example, shown in Figure 1, the second operative position of the insertion element 38 corresponds to a discharge position of the material in an auxiliary container 40.

If it is not possible to discharge it in the melting furnace 12, for example, due to process requirements or conditions connected to the momentary suspension of the melting process, the heated material is discharged into the container

55 auxiliary 40 to allow it to possibly be reinstated later in the melting process, for example, in the heating and transfer apparatus 10.

The conveyor device 13 can be served by monitoring the devices provided to detect at least one blocking condition of the transported material, breakdown of the mechanical monitoring components, volumetric amount of the transported material, weight of the transported material.

The monitoring devices may comprise photocells, TV cameras, optical, inductive, magnetic or similar sensors, possibly controlled and managed by a control unit.

65 According to the embodiment shown in Figures 1 and 8, the melting furnace 12 comprises an electric arc furnace 41 provided with electrodes 42 for supplying electric power and injection devices 43 for

introduce gas, preferably oxygen, capable of promoting fusion and refining reactions.

The electric arc furnace 41 may be provided with introduction means 44 configured to allow the insertion of the heated material.

In particular, the introduction means 44 may comprise a tube, a hopper, vibrating devices or combinations thereof.

In accordance with possible embodiments, which may possibly be combined with the embodiments described herein, the melting plant 11 according to the present invention may also comprise a loading unit 45 located upstream of the heating and transfer apparatus 10 and configured to feed the materials to be heated and transport them to the latter.

The loading unit 45 may comprise at least one of either a conveyor belt, 15 plate conveyor belt, loading basket, hopper, clamping crane, bridge crane or possible combinations thereof.

According to possible embodiments, for example, shown in Figures 1 and 8, the loading unit 45 comprises a conveyor 46 and a loading hopper 47 configured to load a certain amount of scrap onto the conveyor 46.

The loading hopper 47, possibly, can be provided in correspondence with a discharge opening, with a vibrating feeder to measure the amount of material discharged on the conveyor belt 46 and, therefore, to control the delivery rate of material discharged in the heating and transfer apparatus 10.

25 The loading hopper 47 can possibly be served by opening / closing devices 48, such as, for example, a guillotine valve.

The material feed rate can be controlled by modifying the vibration frequency of the vibrating feeder, also according to possible detections that can be made on the conveyor belt 46. In particular, it can be provided to control the weight and / or volume, by detectors suitable installed on conveyor belt 46.

In possible formulations of the present invention, the conveyor belt 46 may be contained at least partially in a container body 49, or housing, to contain the amount of material that is transferred.

On the opposite side where the materials are discharged into the heating and transfer apparatus 10, the container body 49 is provided with an auxiliary discharge opening 50, capable of being selectively opened / closed, to discharge the materials into a container of discharge 51, instead of in the heating and transfer apparatus 10.

It is evident that modifications and / or additions of parts can be made to the heating and transfer apparatus 10 as described so far, without departing from the scope and scope of the present invention.

For example, as shown in Figure 8, the conveyor device 13 may comprise a rotating drum 52, which can selectively rotate about a rotation axis X parallel to the direction of movement D of the materials.

The rotating drum 52 is hollow inside to contain inside the materials to be transferred to the melting furnace 12.

The materials are loaded in correspondence with a first end of the rotary drum 52 and, by rotation of the latter, the forward movement of the materials is defined, in the direction of movement D.

55 According to possible embodiments, the rotating drum 52 may be provided inside with blades configured to determine the forward movement of the materials.

According to a possible embodiment, the rotating drum 52 is inclined to present its insertion end for the materials higher than the discharge end. This allows defining a forward movement of the materials simply due to the effect of gravity.

By properly controlling the inclination angle of the rotating drum 52 and its rotation speed, it is possible to control the supply speed of the materials that are fed to the melting furnace 12.

65 The rotating drum 52 may be made of metallic materials that have low magnetic permeability and low electrical conductivity. Simply by way of example, the material from which the structural part of the

Rotating drum 52 may preferably be austenitic stainless steel coated with heat insulating materials, preferably refractory.

In this embodiment, the induction heating unit 28 comprises at least one coil 29, in

5 in this case two coils 29, spirally wound outside and around the rotating drum 52. In particular, the coils 29 are arranged spaced apart from each other along the length of the rotating drum 52 to control, in a differentiated manner, the heating action to which the latter will be subject during normal operation.

The coils 29 may be substantially similar to those described with reference to the previous embodiments.

Also in this case, the coils 29 are each connected to electric power generators 31, to generate in the materials that are fed an induced magnetic field and respective induced currents suitable for heating the materials.

15 It can be provided that the rotating drum 52 is also provided with other supplementary heat sources, for example, of chemical type such as, for example, burners.

It is also clear that, although the present invention has been described with reference to some specific examples,

A person skilled in the art will certainly be able to achieve many other equivalent forms of the heating and transfer apparatus 10 for metallic materials, having the characteristics as set forth in the claims and, therefore, all being within the scope of the protection defined by them.

Claims (13)

1. Apparatus for heating and transferring mainly metallic materials to a melting furnace (12), said apparatus comprising a conveyor device (13) configured to move said materials continuously to said 5 melting furnace (12), wherein said conveyor device (13) is chosen from a group comprising a conveyor belt, a plate conveyor belt, a mobile board belt, a rotating chamber or a possible combination of the above , wherein said conveyor device (13) is provided with a closed chamber (24) for the passage of said metallic materials, characterized in that it comprises at least one induction heating unit (28) comprising at least one coil (29) externally mounted to said conveyor device (13) and suitable for generating an induced magnetic field in said materials to heat by electromagnetic induction said materials, which move in said conveyor device (13), at a temperature between 300 ° C and 800 ° C, and in any case keeping them in solid state. 2. Apparatus according to claim 1, characterized in that the structural components of said device 15 conveyor (13) are made of materials that have low magnetic permeability and low electrical conductivity.

3.

Apparatus according to claims 1 or 2, characterized in that it comprises several induction heating units (28) associated with the conveyor device (13) in different positions along the longitudinal extension of the latter.

Four.

Apparatus according to any of the preceding claims, characterized in that said coil (19) is defined by a plurality of spirals (30) and that the spirals (30) of the coil (29), or at least some of them, are mechanically attached to the walls of said conveyor device (13), to contain the

25 electromagnetic repulsive forces acting on the coil (29).

5.

Apparatus according to any of the preceding claims, characterized in that said coil (29) is wound around said conveyor device (13) and in accordance with a winding axis substantially parallel to the direction of movement (D) of said materials.

6.

Apparatus according to any of the preceding claims, characterized in that said induction heating unit (28) comprises at least two coils (29) facing each other and between which said conveyor device (13) is interposed, said said arrangements being arranged coils (29) with their winding shafts substantially transverse to the direction of movement (D) of said materials.

7.

Apparatus according to any of the preceding claims, characterized in that said induction heating unit (28) comprises at least one magnetic field concentrating device (32) around which said at least one coil (29) is wound, said device being suitable magnetic field concentrator (32) to concentrate the magnetic field towards said materials.

8.

Apparatus according to claim 7, characterized in that said induction heating unit (28) comprises at least two magnetic field concentrating devices (32) arranged opposite each other, said conveyor device (13) being interposed between said field concentrating devices magnetic (32).

9.

Apparatus according to any of the preceding claims, characterized in that said conveyor device (13) comprises a mobile board conveyor (14) with a mainly longitudinal development, defined by a channel with a concave cross-section of cradle type, to contain the metallic material within it, and associated with a drive element (16) of vibratory type.

10.

Apparatus according to any of the preceding claims, characterized in that a closing body (23) is associated with said conveyor device (13) and is configured to define, by itself or in combination with parts of said conveyor device (13), said Closed chamber (24) for the passage of said materials, with controlled environmental conditions.

eleven.

Apparatus according to any of the preceding claims, characterized in that said conveying device (13) comprises a rotating drum (52) hollow internally to contain said materials within it, said rotating drum (52) being rotatable about a rotation axis (X ) parallel to the direction of movement (D) of said materials.

12.

Melting plant comprising at least one melting furnace (12) in which mainly melting metal materials, a loading unit (45) configured to feed said materials and a heating and transfer apparatus (10) as in any preceding claim , said heating and transfer apparatus (10) being interposed between said loading unit (45) and said melting furnace (12) and being configured to

65 heating and moving said materials, fed by said loading unit (45), to said melting furnace (12), at a temperature between 300 ° C and 800 ° C and, in any case, keeping them in a solid state. 13. Method for melting metal materials comprising transporting, using a conveyor device (13), continuously and to a melting furnace (12), mainly metal materials for melting them, during transport, passing said materials in a closed chamber (24) of said conveyor device (13), characterized in that during the transportation of said materials the heating of said materials is provided by 5 electromagnetic induction at a temperature between 300 ° C and 800 ° C and, in any case, keeping them in a solid state, said heating being achieved by means of an induction heating unit (28) comprising at least one coil (29) which It is mounted externally to the conveyor device (13) and generates an induced magnetic field in said materials.